Video services represent a large majority of the content transported via Internet infrastructures, of the order of 70 to 80%. In particular, on-demand services, in particular in “infra-service” service architectures, better known under the abbreviation OTT (over-the-top service) for video on demand (VoD), require both high throughputs and a guaranteed quality of service. Transmission thereof in the case of multi-spot broadcast (broadcast services) satellites therefore poses a problem, firstly regarding wastage of the resource, which is used several times for the same content, and secondly regarding limiting the impact of the latency introduced by the satellite on account of the transmission times and of the communication protocols implemented with these OTT service architectures.
The prior art describes various systems and methods for optimizing the transportation of these video data.
A first family of solutions is based on cache architectures implemented in the user ground segment. These architectures are designed to vastly improve the transportation and the quality of service offered for this content. However, in this solution, the presence of a cache in the satellite terminals involves a high extra cost for the user ground segment and maintenance and operational issues. In addition, the caches installed on the gateway side are not designed to limit the wastage of resources on the satellite segment.
A second family is based on an architecture that will process, at the satellite, the data on the outward path (gateway to user) and on the return path (user to gateway). The data will be demodulated/decoded, and the resulting data flows managed by a processor on board the satellite. In this context, a cache is used at the satellite to store the data. The decision to cache and the accessing of these data are performed directly by the on-board processor, as is described for example in U.S. Pat. No. 6,697,850. This solution has the drawback of requiring the return path to be regenerated, thereby complicating the payload of the satellite and in particular increasing its bulk and therefore its cost. An alternative solution is described in patent application US20030033355. The principle described consists in demodulating and decoding only the outward path to perform a time delay operation. This solution is therefore not compatible with the need to cache per object in relation to fast-forwarding the VoD. In this case, there is no access on demand, the (live) video stream is transmitted once at the satellite and redistributed to all of the users at a given time slot; there is no request for access from the users, nor congestion control or error recovery.
The system and the method according to the invention are based on a novel approach consisting notably in using, in a particular manner, a cache at the satellite that is associated with proxies positioned at the gateways on the ground, the outward path being processed at the satellite processor, said satellite being considered to be “transparent” for the return path (i.e. the RF signal is simply reamplified without being digitally processed).
The word “content” is used to denote services, data requested by a user, etc.
Users access content in the following manner. A first flow relates to the sending of the video content from a gateway to the satellite for storage at the satellite. When the users wish to access the content, they send a request flow, as far as the gateway, which is then redirected on board (to the satellite) in order then to be processed. Finally, the satellite is able to deliver the content to the terminals that have requested it, or even to other terminals in the same spot if they are able to store it.